More particularly, the invention relates to an engine operating in particular with a cryogenic fluid and, for example, using a device for controlling the stroke of the piston having the effect of stopping the piston at its top dead centre for a period of time and of rotating the engine, and a variable volume active chamber producing work, an integrated (or separate) compression device and a device for recovering ambient temperature thermal energy.
The inventors have filed many patents and patent applications relating to drives and their installations, using gases and more particularly compressed air for a totally clean operation in an urban and suburban site:
WO 96/27737-WO 97/00655-WO 97/39232-WO 97/48884-WO 98/12062-WO 98/15440-WO 98/32963-WO 99/37885-WO 01/69080-WO 03/036088.
To apply these inventions, they have also described in patent application WO 99/63206, to the content of which it is possible to refer, a method and a device for controlling the stroke of the engine pistons making it possible to stop the piston at its top dead centre; a method also described in their patent application WO 99/20881, to the content of which it is also possible to refer, relating to the operation of these engines with single energy or with dual-energy, dual or triple supply modes.
In patent application WO 99/37885, they propose a solution that makes it possible to increase the quantity of energy that can be used and is available, characterized in that the compressed air, before it is inserted into the combustion or expansion chamber, originating from the storage reservoir either directly or after it has passed into the heat exchangers of the ambient temperature thermal energy recovery device, and before it is inserted into the combustion chamber, is channelled into a thermal reheater where, by the increase of its temperature, it will again increase in pressure and/or in volume before it is inserted into the combustion chamber and/or expansion chamber of the engine, thereby again considerably increasing the performance that can be achieved by the said engine.
The use of a thermal reheater, and despite the use of a fossil fuel, has the advantage of being able to use clean continuous combustions that can be catalysed or depolluted by all known means for the purpose of obtaining emissions with infinitesimal pollutants.
The inventors have filed a patent application WO 03/036088, to the content of which it is possible to refer, relating to an additional compressed air injection motor-compressor—motor-alternator set operating on single and multiple energies.
In these types of engine operating with a gas, more particularly with compressed air and comprising a high pressure compressed air reservoir, it is necessary to relieve the compressed air contained in the high pressure reservoir but whose pressure reduces as the reservoir empties to a stable intermediate pressure called the final pressure of use in a buffer tank before it is used in the engine cylinder or cylinders. The well known conventional pressure reducers with valves and springs have very low throughputs and their use for this application requires very heavy and not very efficient apparatus, they are also very sensitive to freezing up due to the humidity of the cooled air during the relief.
To solve this problem, the inventors have also filed a patent application WO 03/089764 relating to a variable rate dynamic pressure reducer for compressed air injection engines, comprising a high pressure compressed air reservoir, and a work tank.
In these pressure reducing devices, the filling of the chamber always represents pressure relief that is harmful to the general output of the machine.
To solve the latter problem, the inventors have also filed a patent application WO 2005/049968 relating to an active chamber engine that uses a device for stopping the piston at top dead centre. It is preferably supplied by compressed air—or any other compressed gas—contained in a high pressure storage reservoir, through a buffer tank called the work tank. The work tank in a dual-energy version comprises a device for reheating the air supplied by an additional energy (fossil or other energy) making it possible to increase the temperature and the volume of the air passing through it. The work tank is therefore an external combustion chamber.
In this type of engine, the expansion chamber inside the engine consists of a variable volume fitted with means making it possible to produce work and is coupled and in contact via a permanent passage with the space lying above the main drive piston. During the stopping of the drive piston at its top dead centre, the pressurized air or gas is let into the active expansion chamber when the latter is at its smallest volume and, under the thrust, will increase its volume while producing work; when the active chamber is substantially at its largest volume, the inlet is then closed and the compressed air still under pressure contained in the active expansion chamber expands in the engine cylinder thereby pushing the drive piston in its downstroke and supplying work in its turn; during the upstroke of the drive piston during the exhaust stroke, the variable volume of the expansion chamber is returned to its smallest volume in order to recommence a complete work cycle.
The thermodynamic cycle of an active chamber engine therefore comprises four phases in compressed air single energy mode:                An isothermal expansion without work        A transfer—slight expansion with work called quasi-isothermal        A polytropic relief with work        An exhaust at quasi-ambient pressure.        
In its dual-energy application and in the additional fuel mode, an air compressor supplies either the high pressure reservoir or the work tank (combustion chamber) or else both volumes in combination.
The active chamber engine can also be produced in single-energy mode with fossil fuel. In a version as described above, the high pressure compressed air storage reservoir is then purely and simply removed and the air compressor directly supplies the work tank that comprises the air reheating device supplied by a fossil or other energy.
The active chamber engine is an engine with an external combustion chamber, however, the combustion in the reheater may be either internal, called “external internal” by bringing the flame directly into contact with the work compressed air, or external, called “external external” by reheating the work air through a heat exchanger.
This type of engine operates in combustion with constant pressure and variable volume according to the relations: PV1=nRT1 and PV2=nRT2Where for constant P, V1/V2=T1/T2
The temperature increase at constant pressure has the effect of increasing in the same proportion the volume of compressed air, and an increase in volume of N times will require an identical temperature increase of N times.
In the dual-energy mode and operating autonomously with additional energy, and when the compressed air is let into the high pressure reservoir, the thermodynamic cycle then comprises seven phases:                Aspiration        Compression        Isothermal expansion in the work tank        Temperature increase        Transfer—slight expansion with work called quasi-isothermal        Polytropic relief with work        Exhaust at quasi-atmospheric pressure        
When the compressed air is let directly into the work tank or combustion chamber, the thermodynamic cycle comprises six phases and becomes:                Aspiration        Compression        Temperature increase        Transfer—slight expansion with work called quasi-isothermal        Polytropic relief with work        Exhaust at quasi-atmospheric pressure        
In this type of engine with dual-energy application, the temperature of the compressed air let into the work tank or combustion chamber takes place at a temperature equal to or greater than the ambient temperature, substantially equal if the compressed air originates from the high pressure storage reservoir and greater if it comes directly from the compressor and the increased volume is achieved in the following phase of the cycle by increase of the pressure.
Originating directly from the compressor, the air temperature may reach, for example, values of the order of 400° C. (673 Kelvin degrees) above the ambient temperature.
To fix ideas, as a nonlimiting example, for the purpose of supplying an active chamber of 30 cm3 at 30 bar, a compressed air load of 5 cm3 at 30 bar and at ambient temperature of 293 K (20° C.) is taken from the storage reservoir in order to be inserted into a work and constant pressure reheating chamber in which, to obtain the required 30 cm3, it is necessary to achieve a combustion that will take the temperature to six times the initial value namely 1758 K or 1485° C.
If the 5 cm3 load originates directly from the compressor, it is substantially at a temperature of 693° K (420° C.) and, for the same result, the temperature of the load must be taken to six times 693 K namely 2158° K or 1885° C.
The use of high temperatures in the external combustion chamber causes numerous stresses in terms of materials and coolings and pollutant emission particularly of NOx (nitrogen oxides) that form above 1000° C.
To solve the latter problem, the inventors have also filed a French patent application No 0506437 (FR-A-2.887.591) relating to a low temperature motor-compressor set with continuous “cold” combustion at constant pressure and with an active chamber that proposes to solve these stresses by allowing, for equivalent performance, much colder combustions which, paradoxically, provide a considerable increase in output of the machine.
The low temperature motor-compressor set with continuous “cold” combustion at constant pressure and with an active chamber comprises a cold chamber making it possible to lower to low or very low temperatures the atmospheric air that supplies the inlet of a compressed air device, that then discharges this compressed work air, still at low temperature, into an external work tank or combustion chamber fitted with an air reheating device, where it considerably increases in volume in order then to be preferably let into an active chamber according to patent application WO 2005/049968 where, during a stop of the drive piston at its top dead centre, the pressurized air or gas is let into the active expansion chamber when the latter is at its smallest volume and, under the thrust, will increase its volume while producing work; when the active chamber is substantially at its largest volume, the inlet is then closed and the still pressurized compressed air contained in the active expansion chamber expands in the engine cylinder thereby pushing the drive piston in its downstroke and providing work in its turn; during the upstroke of the drive piston during the exhaust stroke, the variable volume of the expansion chamber is returned to its smallest volume in order to recommence a complete work cycle.
The thermodynamic cycle of the low temperature motor-compressor set with continuous “cold” combustion at constant pressure and with an active chamber according to French patent application FR 0506437 comprises seven phases:                Considerable reduction of the atmospheric air temperature        Aspiration        Compression        Temperature increase (combustion at constant volume)        Quasi-isothermal transfer        Polytropic relief        Exhaust to the atmosphere at quasi-atmospheric pressure.        